1. Field of the Invention
The present invention relates to wireless communication, and more specifically, to a method and apparatus for applying control information in a wireless communication system.
2. Related Art
Recently, carrier aggregation systems draw attention. Carrier aggregation systems mean systems that configure a broadband by aggregating one or more component carriers (CCs) each having a smaller bandwidth than that of the target broadband when supporting a broadband in a wireless communication system. In the carrier aggregation system, the term “serving cell” may also be used instead of the “component carrier.” Here, a serving cell consists of a downlink component carrier (DL CC) and an uplink component carrier (UL CC) or consists only of a DL CC. In other words, the carrier aggregation system is a system in which a plurality of serving cells is configured for a single terminal.
In the carrier aggregation system, a base station, after configuring a plurality of serving cells for a terminal, may activate or deactivate some of the serving cells as necessary. The terminal receives an activation/deactivation signal for the serving cells, and in response, transmits an ACK/NACK (acknowledgement/non-acknowledgement) signal that is a signal for acknowledging the signal reception. The base station should receive the ACK/NACK signal from the terminal so as to be able to be aware of whether the terminal has exactly decoded the activation/deactivation signal for the serving cells. If receiving an ACK from the terminal, the base station activates the serving cells a predetermined time after receiving the ACK.
That is, in the wireless communication system, the base station may transmit control information that applies from a specific time to the terminal, and the terminal may perform a necessary operation from the specific time using the control information. In this process, the terminal may need to inform the base station through an ACK/NACK (acknowledgement/non-acknowledgement) that the terminal has received the control information and has correctly decoded it. Upon receiving an ACK, the base station may perform an operation by the control information from the specific time, and when receiving an NACK, the base station may resend the control information.
Meanwhile, as a method of transmitting an ACK/NACK, there is ACK/NACK repetition. The ACK/NACK repetition means that an ACK/NACK responding to reception of the same data, rather than being sent only in a single subframe, is repeatedly transmitted a predetermined number of times in a plurality of subframes. The ACK/NACK repetition may also be applicable to an ACK/NACK for control information that applies from a specific time.
However, in the conventional wireless communication systems, when the ACK/NACK repetition applies, the time when the base station is considered to have received an ACK/NACK is ambiguous so that the time when an operation applies under specific control information is unclear. As an example, in the above-described carrier aggregation system, the time when the activation/deactivation information of a serving cell applies is unclear. In general, when the ACK/NACK repetition is used in control information transmission that applies from a specific time, transmission of an ACK/NACK in response thereto, and a process requiring determination of the specific time, the specific time when the control information applies may be vague.